The invention relates to a method for warning the driver of a motor vehicle of a particular situation, which vehicle is equipped with a distance-related cruise control system.
Motor vehicles having a distance-related cruise control system are already available from various manufacturers. A system of this type, offered by the assignee of the present application, for example, under the name “active cruise control,” allows the motor vehicle to move automatically at a desired (or a correspondingly lower) speed while maintaining a defined distance to a motor vehicle traveling in front (such a motor vehicle in front being referred to as a target object). In principle, the active cruise control expands upon the generally known cruise control, which maintains a specific predefined speed, by including an additional distance control function, so that the use of the “active” cruise control is possible even in dense freeway and expressway traffic. This so-called “active cruise control” maintains the predefined desired speed if the vehicle's own lane is clear. If a distance sensor system attached to the motor vehicle, which may operate in particular based on radar, recognizes a target object (such as a motor vehicle traveling ahead) in its own lane, then the motor vehicle's speed is adapted to the speed of the motor vehicle or target object traveling ahead, for example, by applying a suitable braking torque, such that a distance controller contained in the “active cruise control” and/or in the corresponding speed control system automatically maintains a distance to the motor vehicle or target object traveling ahead, which distance is appropriate for the driving situation.
In systems of this type, however, the achievable braking effect, which is generated by the applied braking torque, is limited to a maximum value. For the case in which the achievable braking effect is inadequate for the vehicle to come to a standstill at a safe distance behind a vehicle traveling ahead, it becomes necessary, for example, to make the driver aware of this state. This may be performed by an acoustic signal, for example.
A device for kinesthetic signaling to the driver of a motor vehicle, which is triggered when a shutoff is imminent of the distance-related cruise control system, which is intended or caused by a functional disturbance, or when a required braking effect may not be applied by the control system, is known from DE 198 57 992. The kinesthetic signaling in DE '992 is performed by activating the deceleration unit in such a manner that the motor vehicle experiences an oscillating deceleration, which is sensed by the driver.
“Active cruise control” systems of the above-mentioned type are only usable in a speed range of approximately from 30-180 km/h. In the speed range below 30 km/h, such a system is not activatable or shuts off automatically according to a specific algorithm. Stationary target objects also may not be used by the system, or may only be used in a limited way for the control.
To also be able to use a speed control system having a distance sensor system in the speed range below 30 km/h, for example, in particular in traffic jam situations, requires that a sensor viewing range be expanded by additional sensors. Furthermore, an algorithm must be able to differentiate between relevant stationary and traveling target objects. One possible system implementation may include differentiating between a typical control range, in which no reaction to stationary targets occurs, and a stop-and-go range, in which stationary target objects are reacted to. This so-called stop-and-go range may have an upper speed restriction limiting value, e.g., in the magnitude of 30 km/h. A distance-related cruise control system expanded in this manner is known, for example, from DE 101 51 717 A1.
In systems of this type, without additional technical features, the possibility exists that the driver, while the motor vehicle was kept stationary by an applied braking torque via the distance-related cruise control system, will get out of the vehicle and forget that the vehicle is only kept stationary because of the active control. In current systems, the driver is usually made aware of this circumstance using an acoustic and/or visual signal.
The object of the invention is to specify a method for warning the driver in a hazard situation, as described above, which is improved in regard to the perceptibility of the warning signal.
According to the invention, a method is provided for warning the driver of a motor vehicle, which is equipped with a distance-related cruise control system, of a hazard situation. With such a distance-related cruise control system, the motor vehicle is kept at a standstill during the distance-related cruise control using an applied braking torque. The method recognizes the leaving of the motor vehicle, or an intention of the driver to leave the motor vehicle. When the method recognizes a leaving the motor vehicle, or upon recognizing an intention to leave the motor vehicle, the applied braking torque is changed and/or modulated in such a manner that the motor vehicle experiences a movement and/or oscillation that is perceptible to the driver.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description when considered in conjunction with the accompanying drawing.